Data-driven understanding of cybersecurity posture is an important problem
that has not been adequately explored. In this paper, we analyze some real data
collected by CAIDA's network telescope during the month of March 2013. We
propose to formalize the concept of cybersecurity posture from the perspectives
of three kinds of time series: the number of victims (i.e., telescope IP
addresses that are attacked), the number of attackers that are observed by the
telescope, and the number of attacks that are observed by the telescope.
Characterizing cybersecurity posture therefore becomes investigating the
phenomena and statistical properties exhibited by these time series, and
explaining their cybersecurity meanings. For example, we propose the concept of
{\em sweep-time}, and show that sweep-time should be modeled by stochastic
process, rather than random variable. We report that the number of attackers
(and attacks) from a certain country dominates the total number of attackers
(and attacks) that are observed by the telescope. We also show that
substantially smaller network telescopes might not be as useful as a large
telescope